Look under the starter (you have to remove the starter for this). You will see a number like D1OE-6015-B. C=60's, D=70's, E=80's, F=90's. Second digit is year of decade. so the original casting of the above numder is 71. There will be a date code: 1B15 which is 1=71 (following casting number above) B=Feb (A=Jan, M=Dec, no I) and 15 is the day.